Coal has a small percentage of hydrocarbons trapped within it. As coal is heated, these hydrocarbons "gas off" and accumulate in the fire chamber and chimney system. If the volatile gases have the proper fuel/air mixture they can/will explode. Don't fear, there are many ways to prevent it.Spacecadet wrote: ↑Tue. Feb. 20, 2018 2:40 amMy goal is to not do this again...had to put the baro back in the pipe and climb on to the roof to put the chimney cap back on. I fortunately had the ash door open... so it could have been worse.
The method I use is to leave the load door cracked open a smidgen. Not much though since you still need combustion air to come up thru the grates to recover the fire and get the fresh batch burning. The cracked open load door allows air in over the fire to keep the volatile gases diluted so that they don't have the proper fuel/air mixture to explode. The blue flames will safely appear over the fuel bed when it's ready.
Maybe others will chime in with their puff back prevention techniques.